Turbofan

About: Turbofan is a research topic. Over the lifetime, 4114 publications have been published within this topic receiving 39490 citations. The topic is also known as: fanjet & turbofan engine.

Design and Construction of a Two Shaft Test Turbine for Investigation of Mid Turbine Frame Flows

Abstract: In order to reduce the specific fuel consumption and consequently to minimise the CO2 emission of aircraft turbine engines, development and integration of a contra-rotating open rotor architecture and the geared turbofan concept are promising alternatives to the classical turbofan engines. The large dimensions of future contra-rotating fans lead to lower rotational speed and furthermore a bigger size of the powering low pressure stages. Therefore the flow leaving the high pressure turbine (HPT) has to be guided to the low pressure turbine (LPT) inlet at larger diameter, if possible without interference or separation. To minimise weight and costs of the aircraft engine the flow diverting mid turbine frame (MTF) has to be designed preferable short. Except for flow redirection this intermediate duct has to transfer the forces from the turbine bearings of both shafts to the turbine casing and further to the engine mount. Therefore the flow channel has to be equipped with thick rigid struts. These struts may also be used to accelerate the flow and take the function of the inlet vanes. In that case this so called integrated concept helps to reduce engine weight and length. One goal of the EU project DREAM is to analyse the flow through such a MTF with turning struts and a downstream arranged counter rotating LPT. The investigation of these complex interrelationships needs a test facility with engine representative conditions. To perform these investigations the continuously operating transonic test turbine facility (TTTF) at Graz University of Technology has been adapted. This test setup consists of a redesigned HPT, a new developed single-stage LPT and a turning mid turbine frame (TMTF). The aerodynamic design of the first setup was performed by MTU Aero Engines. The shafts of both turbines are mechanically independent, so the test rig allows a realistic two shaft turbine operation. To examine the highly 3-dimensional flow through the TMTF and the downstream LPT detailed measurements will be performed with conventional measurement techniques (temperature and pressure rakes, static pressure taps), oil flow visualisation as well as with 5-hole-probes for steady and fast response aerodynamic probe (FRAP) for unsteady measurements. Optical and acoustical measurements are planned to be used in following projects.

Theoretical implications of Active Noise Control for turbofan engines

Abstract: The objective of this stud)' is to develop the analytical tools that will allow the assessment of the feasibility of using Active Noise Control (ANC) in aircraft engine ducts to suppress radiated tones. It is assumed that the active noise control system will operate using the "noise cancellation'' principle, such that control sound source transducers will inject sound into the duct that directly interferes with the sound generated by the turbomachinery sources. The approach will be to develop the theory needed bused on duct modal analysis. In addition, it is hoped that an analytical approach f o r assessing the feasibility of aircraft engine ANC systems may also provide some guidance for the design optimization of such systems. Analyses are developed for the circumferential and radial mode coupling of wall-mounted sources to a cylindrical duct. A sample case is included that examines energy requirements for ANC source generation.

Air dryer system and method employing a jet engine

Abstract: An air dryer and process employs a jet engine for producing high quality dried products. A turbofan jet engine in an air-drying system uses both thermal and non-thermal air-drying. The turbofan jet engine is housed within an air distribution chamber for directing exhaust air and bypass air from the jet engine into a product drying tube, where it is dried through a combination of thermal drying from heat content in an engine exhaust, and by the kinetic energy of air flowing past the product traveling through the drying tube, that may include a physical impediment for retarding retard the speed of the product solids flowing in the air stream through the tube.

An Assessment of Gas Foil Bearing Scalability and the Potential Benefits to Civilian Turbofan Engines

Abstract: Over the past several years the term oil-free turbomachinery has been used to describe a rotor support system for high speed turbomachinery that does not require oil for lubrication, damping, or cooling. The foundation technology for oil-free turbomachinery is the compliant foil bearing. This technology can replace the conventional rolling element bearings found in current engines. Two major benefits are realized with this technology. The primary benefit is the elimination of the oil lubrication system, accessory gearbox, tower shaft, and one turbine frame. These components account for 8 to 13 percent of the turbofan engine weight. The second benefit that compliant foil bearings offer to turbofan engines is the capability to operate at higher rotational speeds and shaft diameters. While traditional rolling element bearings have diminished life, reliability, and load capacity with increasing speeds, the foil bearing has a load capacity proportional to speed. The traditional applications for foil bearings have been in small, lightweight machines. However, recent advancements in the design and manufacturing of foil bearings have increased their potential size. An analysis, grounded in experimentally proven operation, is performed to assess the scalability of the modern foil bearing. This analysis was coupled to the requirements of civilian turbofan engines. The application of the foil bearing to larger, high bypass ratio engines nominally at the 120 kN (approx.25000 lb) thrust class has been examined. The application of this advanced technology to this system was found to reduce mission fuel burn by 3.05 percent.

A Comparative Study of Genetic Algorithms and Gradient Methods for RM12 Turbofan Engine Diagnostics and Performance Estimation

Abstract: Recent work on gas turbine diagnostics based on optimisation techniques advocates two different approaches: 1) Stochastic optimisation, including Genetic Algorithm techniques, for its robustness when optimising objective functions with many local optima and 2) Gradient based methods mainly for their computational efficiency. For smooth and single optimum functions, gradient methods are known to provide superior numerical performance. This paper addresses the key issue for method selection, i.e. whether multiple local optima may occur when the optimisation approach is applied to real engine testing. Two performance test data sets for the RM12 low bypass ratio turbofan engine, powering the Swedish Fighter Gripen, have been analysed. One set of data was recorded during performance testing of a highly degraded engine. This engine has been subjected to Accelerated Mission Testing (AMT) cycles corresponding to more than 4000 hours of run time. The other data set was recorded for a development engine with less than 200 hours of operation. The search for multiple optima was performed starting from more than 100 extreme points. Not a single case of multi-modality was encountered, i.e. one unique solution for each of the two data sets was consistently obtained. The RM12 engine cycle is typical for a modern fighter engine, implying that the obtained results can be transferred to, at least, most low bypass ratio turbofan engines. The paper goes on to describe the numerical difficulties that had to be resolved to obtain efficient and robust performance by the gradient solvers. Ill conditioning and noise may, as illustrated on a model problem, introduce local optima without a correspondence in the gas turbine physics. Numerical methods exploiting the special problem structure represented by a non-linear least squares formulation is given special attention. Finally, a mixed norm allowing for both robustness and numerical efficiency is suggested.Copyright © 2004 by ASME